In the existing Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, there are multiple cache queues (four cache queues currently) inside a station that can access a wireless local area network (WLAN), and the station temporarily stores service data with different priorities into different cache queues. Each cache queue is associated with one access category (AC), and a service data with a higher priority is temporarily stored by the station into a cache queue corresponding to an AC with a higher priority. Each AC is used to maintain one backoff counter, which is configured to contend for a transmission channel. In addition, an AC is corresponding to an enhanced distributed channel access function (EDCAF) in the station. The EDCAF is a logical function module in the station and is configured to control when data of the AC corresponding to the EDCAF is sent. Generally, when a station needs to transmit data of an AC, the station needs to contend with another station for a channel to transmit the data of the AC. When a clear channel assessment (CCA) result obtained by the station by listening is that a channel is in an idle state, a backoff counter starts to back off. When the backoff counter maintained by using the AC corresponding to data that needs to be transmitted by the station backs off to 0, the station obtains a transmission opportunity (TXOP) by initializing a frame exchange procedure, to transmit the data of the AC. The TXOP is a time length for occupying a channel by the station.
At present, an implementation of the IEEE 802.11 standard is as follows: After obtaining a TXOP for an AC, a station may transmit data of the AC once or for many times. After transmission of the data of the AC is completed, a channel is released by sending a CF-End frame.
However, in a prior-art data transmission method, a channel is released after transmission of data corresponding to an AC for which the channel is obtained by means of contention is completed, wasting a channel resource, and further affecting data transmission efficiency of a system.